Summer was a season.
The exploding warp core engines of a Rutan ship created a time bubble around Stockbridge. Millennia passed inside it, but it was always summer. The Fifth Doctor, Nyssa and Maxwell Edison "popped" the bubble, finally bringing autumn to the town. (AUDIO: The Eternal Summer)
After escaping its imprisonment by the Time Lords, the Kin went to Earth in the summer of 1984. It started buying property using money recycled through time to attract the Eleventh Doctor as part of its plan to control all time. (PROSE: Nothing O'Clock)
In 2011, Amy Pond and Rory Williams spent "all summer" waiting for the Eleventh Doctor as he searched for their daughter, Melody Pond. Ultimately, the Doctor returned to Leadworth empty-handed, only for the three to subsequently learn that Melody had regenerated into Mels, Amy and Rory's childhood friend. (TV: Let's Kill Hitler)